Fuel control systems

ABSTRACT

A fuel control system for an internal combustion engine comprising sensing devices for sensing the quantities of oxygen and carbon monoxide or unburnt hydrocarbons in the engine exhaust emission, a temperature measuring device, a control device for controlling the rate of supply of fuel to the engine in accordance with at least one engine parameter and apparatus controlled by the sensing devices and by the temperature measuring device so as to modify the rate of fuel supply in accordance with the quantity of carbon monoxide or unburnt hydrocarbon in the exhaust emission when the engine temperature is below a predetermined value and in accordance with the quantity of oxygen in the exhaust emission when the engine temperature is above the predetermined temperature.

' United States Patent Williams FUEL CONTROL SYSTEMS PrimaryExaminer-Wendell E. Burns 75 Inventor: Malcolm William S l'h ll, E l d 1O i u ng an Assistant E raminerRonald B. Cox [73] Ass1gnee: The LucasElectrical Company Attorney, Agent, or Firm-Waters, Schwartz & NissenLimited, Birmingham, England [22] Filed: May 3, 1974 [57] ABSTRACT [21]Appl. No.: 466,886 A fuel control system for an internal combustionengine comprising sensing devices for sensing the quantities of oxygenand carbon monoxide or unburnt hy- [301 Forelgn Appllc au0n Pl-mmy Datadrocarbons in the engine exhaust emission, a tempera- May 1973 UmtedKmgdom 21446/73 ture measuring device, a control device for controllingthe rate of supply of fuel to the engine in accordance [52] 123/32 EA;123/139 E; 60/276 with at least one engine parameter and apparatus con-[Sl] llli. Cl. FOZB 3/00; FOZM 39/00 trolled by the Sensing devices andb the temperature [58] new of Search 123/32 139 179 measuring device soas to modify the rate of fuel sup- 123/179 G; 60/276 ply in accordancewith the quantity of carbon monoxide or unburnt hydrocarbon in theexhaust emission [561 References C'ted when the engine temperature isbelow a predeter- UNITED STATES PATENTS mined value and in accordancewith the quantity of 3,738,341 6/1973 LOOS t 1 60/276 Oxygen in theexhaust mission when the engine 3,745,768 7/1973 Zechnall 123/32 EAperature is above the predetermined temperature.

3,768,259 10/1973 Carnahan 1 60/276 3,827,237 8/1974 Linder 60 276 6Chums, 2 Drawmg Figures THENQETTLE LE TRANSDUCER ENGINE V l I SPEEDCONTROL TRANSDUCER DEV'CE ENGNE CONTROL COMPARATOR TEMPERATURE CIRCUI; 2l

TRANSDUCER )Zl I9 I LOGIC 20 UNIT Low PASS FILTERS UNBURNT HYDROCARBONSENSOR US. Patent Dec. 16, 1975 3,926,154

THROTTLE ANGLE Q I O TRANSDUCER ENGINE CONTROL 4 SPEED E DEVICETRANSDUCER I3 CONTROL COMPARATOR ENGINE TEMPERATURE CIRCUIp 2 ITRANSDUCER I i LOGIC 2O UN)IT LOW PASS FILTERS OXYGEN sENsoR I5 I4UNBURNT [j HYDROCARBON sENsoR FIG.I

RELATIVE POLLUTANT AIR/FUEL RATIO FIG.2

FUEL CONTROL SYSTEMS This invention relates to fuel control systems foruse with internal combustion engines and has as its object the provisionof such a system in a convenient form.

The invention resides in a fuel control system for use with an internalcombustion engine comprising means for sensing the quantity of oxygenwithin the exhaust emission of the engine, means forsensing the quantityof carbon monoxide or unburnt hydrocarbon within the exhaust emission,means for measuring the temperature of the engine, and control means forcontrolling the rate of supply of fuel to the engine in accordance withat least one engine parameter and means for modifying the quantity offuel fed to the engine in accordance with the quantity of carbonmonoxide or unburnt hydrocarbon within the exhaust emission when theengine temperature is below a predetermined value and in accordance withthe quantity of oxygen within the exhaust emission when the enginetemperature is above said predetermined value.

The invention will now be more particularly described with reference tothe accompanying drawings wherein:

FIG. 1 is a block circuit diagram illustrating one embodiment of a fuelcontrol system according to the present invention, and

FIG. 2 is a graph of the relative pollutant in the exhaust emission ofan engine plotted against the air/fuel ratio of the engine.

Referring to FIG. 1, the fuel control system shown therein comprises acontrol device which produces an electrical output pulse on a line 11 toan injector. The length of the electrical output pulse determines thetime for which the injector allows fuel to pass from a pump into theengine, and hence the rate at which fuel is fed to the internalcombustion engine. The control device 10 is programmed such that thelength of the electrical output pulse is dependent upon the values oftwo engine parameters, namely the throttle angle and the engine speedand to this end a transducer 12 is provided for feeding the signalrepresentative of the throttle angle to the control device 10, and-atransducer 13 is provided for feeding a signal representative of theengine speed to the control device 10.

Means are also provided for modifying the length of the electricaloutput pulse in accordance with the nature of the exhaust emission ofthe internal combustion engine. Such means comprises an oxygen sensor 14and an unburnt hydrocarbon sensor 15. The sensors 14 and 15 produceelectrical signals, the amplitude of which are representative of thequantity of oxygen within the exhaust emission and the quantity ofunburnt hydrocarbon within the exhaust emission respectively. Thesesignals are fed to low pass filters 16 and 17 respectively, which serveas averaging circuits, and the output of the two low pass filters l6 and17 are fed to a logic unit 18. A transducer 19 is provided for producinga signal representative of the engine temperature and this signal is fedon the one hand to the logic unit 18 and on the other hand to a controlcircuit 20. The logic unit 18 connects the output from the low passfilter 17 to a first input of a comparator 21 when the output of thetransducer 19 is below a predetermined value, representing a set hotengine temperature, and connects the output of the low pass filter 16 tosaid first input of the comparator 21 when the output of the transducer19 is above said predetermined value. The control device 20 produces anoutput which varies in accordance with the engine temperature; and whichis representative of the required air/fuel ratio of the engine, and thisoutput from the control circuit 20 is fed to a second input of thecomparator 21.

Now referring to the graph shown in FIG. 2, B is a curve of unburnthydrocarbon content of the exhaust emission plotted against air/fuelratio, and C is a curve of oxygen content of the exhaust emissionplotted against air/fuel ratio. Thus, it will be seen that when theair/fuel ratio is on the rich side of the stoichiometric line (indicatedby the reference numeral 22 in FIG. 2) a measure of the unburnthydrocarbon content in the exhaust emission will produce a signalrepresentative of the air/fuel ratio of the engine, and when theair/fuel ratio is on the lean side of the stoichiometric line 22 thenthe measure of the oxygen content in the exhaust emission will produce asignal representative of the air/fuel ratio of the engine. Now inpractice, the air/fuel ratio of the engine will only be on the rich sidewhen the engine temperature is low that is to say during initial warm-upof the engine, and once the engine temperature has achieved its normaloperating temperature then air/fuel ratio will be on the lean side ofthe stoichiometric line 22. Thus, during engine warm-up the logic unit18 connects the unburnt hydrocarbon sensor 15 to said first input of thecomparator 21 which compares the actual air/fuel ratio of the enginewith the required air/fuel ratio of the engine and produces an outputwhich is connected to the control device 10 for modifying the length ofthe electrical output from the device 10 and thereby adjusting thequantity of fuel fed to the engine. When the engine has reached itsnormal operating temperature, the logic unit 18 connects the oxygensensor 14 to said first input of the comparator 21 and once again theelectrical output pulse of the device 10 is modified in accordance withthe difference between the signals of the two inputs of the comparator21.

Finally, it is to be appreciated that instead of using an unburnthydrocarbon sensor, a carbon monoxide sensor could be used, A being acurve of carbon monoxide content of the exhaust emission plotted againstair/fuel ratio.

The invention may also be applied to fuel system in which a variablespeed fuel pump continuously injects fuel into the engine air intake ata rate determined by the control system.

I claim:

1. A fuel control system for an internal combustion engine comprisingmeans for sensing the quantity of oxygen within the exhaust emission ofthe engine, means for sensing the quantity of carbon monoxide or unburnthydrocarbon within the exhaust emission, means for measuring thetemperature of the engine, control means for controlling the rate ofsupply of fuel to the engine in accordance with at least one engineparameter, and operation means coupled to said engine temperaturemeasuring means and to said control means for modifying the quantity offuel fed to the engine in accordance with engine temperature and thequantity of carbon monoxide or unburnt hydrocarbon within the exhaustemission when the engine temperature is below a predetermined value andin accordance with the quantity of oxygen within the exhaust emissionwhen the engine temperature is above said predetermined value.

2. A fuel control system as claimed in claim 1 in which said means forsensing the quantity of oxygen and said means for sensing the quantityof carbon monoxide or unburnt hydrocarbon, each comprises a sensingdevice which produces an electrical output signal the amplitude of whichis representative of the quantity of the appropriate gas.

3. A fuel control system as claimed in claim 2 including a low passfilter for each sensing device connected to reject high frequencycomponents in said electrical output signals.

4. A fuel control system as claimed in claim 1 wherein said operationmeans includes logic means coupled to said engine temperature measuringmeans and to said oxygen sensing means and the sensing means for carbonmonoxide or unburnt hydrocarbons for passing a signal from a selectedone of said sensing means depending on whether the engine temperature isabove or below said predetermined value.

5. A fuel control system as claimed in claim 4 wherein said operationmeans further comprises a comparator connected to said logic means forreceiving the signal passed thereby, and means coupled to said enginetemperature measuring means and to said comparator to provide a secondsignal to the comparator indicative of the required air/fuel ratio atthe particular engine temperature which is measured.

6. A fuel control system as claimed in claim 1 wherein said controlmeans includes means for making the air/fuel ratio relatively rich whenengine temperature is low and for making the air/fuel ratio relativelylean when engine temperature is high.

1. A FUEL CONTROL SYSTEM FOR AN INTERNAL COMBUSTION ENGINE COMPRISINGMEANS FOR SENSING THE QUANTITY OF OXYGEN WITHIN THE EXHAUST EMISSION OFTHE ENGINE MEANS FOR SENSING THE QUANTITY OF CARBON MONOXIDE OR UNBURNTHYDROCARBON WITHIN THE EXHAUST EMISSION, MEANS FOR MEASURING THETEMPERATURE OF THE ENGINE, CONTROL MEANS FOR CONTROLLING THE RATE OFSUPPLY OF FULE TO THE ENGINE IN ACCORDANCE WITH AT LEAST ONE ENGINEPARAMETER, AND OPERATION MEANS COUPLED TO SAID ENGINE TEMPERATUREMEASURING MEANS AND TO SAID CONTROL MEANS FOR MODIFYING THE QUANTITY OFFUEL TO THE ENGINE IN ACCORDANCE WITH ENGINE TEMPERATURE AND THEQUANTITY OF CARBON MONOXIDE OR UNBURNT HYDROCARBON WITHIN THE EXHAUSTEMISSION WHEN THE ENGINE TEMPERATURE IS BELOW A PREDETERMINED VALUE ANDIN ACCORDANCE WITH THE QUANTITY OF OXYGEN WITHIN THE EXHAUST EMISSIONWHEN THE ENGINE TEMPERATURE IS ABOVE SAID PREDETERMINED VALUE.
 2. A fuelcontrol system as claimed in claim 1 in which said means for sensing thequantity of oxygen and said means for sensing the quantity of carbonmonoxide or unburnt hydrocarbon, each comprises a sensing device whichproduces an electrical output signal the amplitude of which isrepresentative of the quantity of the appropriate gas.
 3. A fuel controlsystem as claimed in claim 2 including a low pass filter for eachsensing device connected to reject high frequency components in saidelectrical output signals.
 4. A fuel control system as claimed in claim1 wherein said operation means includes logic means coupled to saidengine temperature measuring means and to said oxygen sensing means andthe sensing means for carbon monoxide or unburnt hydrocarbons forpassing a signal from a selected one of said sensing means depending onwhether the engine temperature is above or below said predeterminedvalue.
 5. A fuel control system as claimed in claim 4 wherein saidoperation means further comprises a comparator connected to said logicmeans for receiving the signal passed thereby, and means coupled to saidengine temperature measuring means and to said comparator to provide asecond signal to the comparator indicative of the required air/fuelratio at the particular engine temperature which is measured.
 6. A fuelcontrol system as claimed in claim 1 wherein said control means includesmeans for making the air/fual ratio relatively rich when enginetemperature is low and for making the air/fuel ratio relatively leanwhen engine temperature is high.